In an Orthogonal Frequency Division Multiplexing (OFDM) system, data are time-frequency dimensional, therefore, multiplexing carried out between a control channel and a service channel can be in the time direction and the frequency direction, that is, there are two multiplexing modes available: Time Division Multiplex (TDM) and Frequency Division Multiplex (FDM). In an LTE or LTE-A system, a Resource Block (RB; an RB mapped to a physical resource is known as a physical resource block) is defined as OFDM symbols in a continuous slot in time domain and 12 or 24 continuous subcarriers in frequency domain, therefore, one RB consists of Nsymb*NSCRB Resource Elements (REs), wherein Nsymb represents the number of the OFDM symbols in one slot, and NSCRB represents the number of the continuous subcarriers of an RB in the frequency domain.
An LTE system, an LTE-A system and an International Mobile Telecommunication Advanced (IMT-Advanced) system are all based on an OFDM technology, and data are time-frequency dimensional in an OFDM system, however, in order to lower the power consumption of a UE, the control channel generally adopts TDM mode, in other words, the control channel and the service channel are separated in time from each other, for instance, if there are 14 OFDM symbols in a subframe and the first one, two, three or four OFDM symbol(s) can be taken as a control channel, then the following 13, 12, 11 or 10 OFDM symbols can be correspondingly taken as a service channel.
An explanation is given below firstly by taking a control channel of a current LTE system as an example, for instance, in an LTE system, downlink control signaling mainly includes the following contents:
1) a Physical Control Format Indicator Channel (PCFICH);
2) DownLink Grant (DL grant);
3) UpLink Grant (UL grant);
4) a Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH);
it can be seen that a control channel is composed of different parts, each of which has a specific function. For the sake of a convenient description, the following terms and conventions are defined:
1) several OFDM symbols are indicated to serve as a control channel (namely, a PCFICH), independent from Control Channels Elements (CCE), wherein the PHICH is also independent from the CCE;
2) L continuous subcarriers in the frequency domain are referred to as the CCE, which may include the DL grant and the UL grant;
3) each CCE is modulated through Quadrature Phase Shift Keying (QPSK) modulation;
4) each control channel consists of one CCE or multiple CCEs;
5) each UE can monitor a series of candidate control channels;
6) the number of candidate control channels is the maximum time of blind detections;
7) the number of candidate control channels is greater than that of the CCEs;
8) several combinations are specified for a receiving end and a transmitting end, for instance, only the combinations of 1, 2, 4 or 8 CCE(s) are taken as the candidate control channel;
9) the combinations of 1, 2, 4 or 8 CCE(s) may correspond to different code rates, respectively.
At an eNode-B, control information of each UE is subjected to channel coding and then sequentially to QPSK modulation, to mapping from a CCE to an RE and to Inverse Fast Fourier Transform (IFFT), and then it is sent out; provided that the control channel here consists of 32 CCEs, after the receiving end completes Fast Fourier Transform (FFT), the UE starts to carry out a blind detection starting from the combination of 1 CCE (that is, respectively carrying out a blind detection on CCE0, CCE1, . . . CCE31), or starting from the combination of 2 CCEs (that is, respectively carrying out a blind detection on [CCE0, CCE1], [CCE2, CCE3], . . . [CCE30, CCE31]) if the monitoring on a UE_ID is failed, and so forth. The UE is switched to a sleep mode if it monitors no UE_ID matching with itself during the whole blind detection process, which means no distribution of control signaling to the UE at this time, or the UE demodulates corresponding service information according to control signaling if it monitors a matched UE_ID.
The research object of B3G/4G is to provide a user with wireless transmission with a peak rate as high as 100 MPs and 1 Gbps respectively in a high-speed and low-speed mobile environment by pooling a cellular access system, a fixed wireless access system, a nomadic access system and a wireless area network and other access systems in combination with an all-IP network, and to realize seamless connection of a cellular system, a local wireless network, broadcast and television and satellite communications so that people can communicate with any other one in any way at any place and at any time. A relay technology, which can be applied as an effective measure, can improve both the coverage and the capacity of a cell.
An inband-relay means that a link from an eNode-B to a relay node and a link from the relay node to a User Equipment (UE) are operative on the same frequency resource. However, since a transmitter of an inband-relay node will cause interference (self-interference) on a receiver of the inband-relay node, it is impossible that the link from the eNode-B to the relay node and the link from the relay node to the UE are operative synchronously on the same frequency resource unless signal separation and antenna isolation are great enough. Similarly, the relay node cannot send the eNode-B data while receiving data from the UE.
In accordance with the regulations in a current LTE system, a 10 ms radio frame consists of 10 subframes of length 1 ms, which may comprise unicast subframes and multicast broadcast subframes, wherein if Frequency Division Duplex (FDD) mode is adopted, subframes #0 and #5 are used for sending synchronous signals, and subframes #4 and #9 are used for paging; and if Time Division Duplex (TDD) mode is adopted, subframes #0 and #5 are used for sending synchronous signals, and subframes #1 and #6 are used for paging, that is, FDD subframes (#0, #4, #5 and #9) and TDD subframes {#0, #1, #5 and #6} are dedicatedly used for the aforementioned specific purposes, therefore they cannot be used for distribution of subframes in a Multicast Broadcast Single Frequency Network (MBSFN), in other words, there are at most 6 distributable MBSFN subframes in a radio frame.
A possible solution to the receiving-sending interference problem is to forbid a relay node sending data to a UE while the relay node is receiving data from an eNode-B, that is, to add, after relaying to a UE link, a guard gap which is only for a conversion from a receiving state to a sending state or an inverse conversion but not for any other operation. MBSFN subframes are currently adopted in an LTE to transmit relay subframes in the following specific way: a Multimedia Broadcast Multicast Service (MBMS) Control Entity (MCE) first configures available MBSFN subframes for an eNode-B, then the eNode-B configures available relay subframes in the available MBSFN subframes. Therefore, on downlink, a relay node first sends its subordinate UE control information (including feedback information Acknowledgment/Negative Acknowledgement (ACK/NACK) of uplink transmission data and UL grant information)) at the first 1 or 2 OFDM symbol(s), then completes switching from a sending state to a receiving state in the time range ‘gap’, and at last receives data from the eNode-B at the following OFDM symbols.
Currently, the research on using an MBSFN subframe as a relay subframe has been a hot object, while the research on a specific control channel structure and a mapping manner of a link from an eNode-B to a relay node (RN) is still blank. In addition, on downlink, an RN first sends control information to its subordinate UE at the first 1 or 2 OFDM symbol(s) while an eNode-B sends control information to a directly-connected UE at the first 1, 2, 3 or 4 OFDM symbol(s), therefore, the RN cannot receive the control information of the link from the eNode-B to the RN at the first 1 or 2 OFDM symbol(s). The present invention is just proposed to address such problems.